Thin film magnetic recording disks and disk drives are conventionally employed for storing large amounts of data in magnetizable form. In operation, a typical contact start/stop (CSS) method commences when a data transducing head begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk where it is maintained during reading and recording operations. Upon terminating operation of the disk drive, the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the disk. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic operation consisting of stopping, sliding against the surface of the disk, floating in the air, sliding against the surface of the disk and stopping.
For optimum consistency and predictability, it is necessary to maintain each transducer head as close to its associated recording surface as possible, i.e., to minimize the flying height of the head. Accordingly, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to excessive stiction and friction during the start up and stopping phases, thereby causing wear to the head and recording surfaces, eventually leading to what is referred to as a "head crash." Thus, there are competing goals of reduced head/disk friction and minimum transducer flying height.
Conventional practices for addressing these apparent competing objectives involve providing a magnetic disk with a roughened recording surface to reduce the head/disk friction by techniques generally referred to as "texturing." Conventional texturing techniques involve mechanical polishing or laser texturing the surface of a disk substrate to provide a texture thereon prior to subsequent deposition of layers, such as an underlayer, a magnetic layer, a protective overcoat, and a lubricant topcoat, wherein the textured surface on the substrate is intended to be substantially replicated in the subsequently deposited layers.
A typical longitudinal recording medium is depicted in FIG. 1 and comprises a substrate 10, typically an aluminum (Al)-alloy, such as an aluminum-magnesium (Al-Mg)-alloy, plated with a layer of amorphous nickel-phosphorus (NiP). Alternative substrates include glass, glass-ceramic materials and graphite. Substrate typically contains sequentially deposited on each side thereof a chromium (Cr) or Cr-alloy underlayer 11, 11', a cobalt (Co)-base alloy magnetic layer 12, 12', a protective overcoat 13, 13', typically containing carbon, and a lubricant topcoat 14, 14'. Cr underlayer 11, 11' can be applied as a composite comprising a plurality of sub-underlayers 11A, 11A'. Cr underlayer 11, 11', Co-base alloy magnetic layer 12, 12' and protective overcoat 13, 13', typically containing carbon, are usually deposited by sputtering techniques performed in an apparatus containing sequential deposition chambers. A conventional Al-alloy substrate is provided with a NiP plating, primarily to increase the hardness of the Al substrate, serving as a suitable surface to provide a texture, which is substantially reproduced on the disk surface.
In accordance with conventional practices, a lubricant topcoat is applied over the protective layer to prevent wear between the disk and head interface during drive operation. Excessive wear of the protective overcoat increases friction between the head and disk, thereby causing catastrophic drive failure. Excess lubricant at the head-disk interface causes high stiction between the head and disk. If stiction is excessive, the drive cannot start and catastrophic failure occurs. Accordingly, the lubricant thickness must be optimized for stiction and friction.
Magnetic recording media are typically lubricated by applying a topcoat lubricant including perfluoroalkylpolyethers or their derivatives. Conventionally, these lubricants are applied by a dip lubrication method, which method involves dissolving the lubricant in a solvent to form a lubricant solution and submerging the recording media in the lubricant solution to form a topcoat thereon. Dip lubrication processes consumes large quantities of solvent and are economically and environmentally costly. Thus, to overcome the inherent deficiencies of conventional lubrication processes, solvent free processes which provide high performance topcoat lubricants are highly sought and desirable.
Gui et al., in U.S. Pat. No. 5,562,965, disclose a process of coating thin film discs by vapor depositing a terminally finction perfluoroalklpolyether lubricant on the disc Requiring high temperature and amient pressure. However, deposition of lubricants under the conditions of elevated temperature and ambient pressure introduces a variety of deleterious results in the performance of the applied topcoat lubricant. For example, under such conditions lubricants may experience oxidative degradation and, consequently, the deposited lubricants do not achieve optimum performance. Further, it is extremely difficult to deposit uniform coatings and to control the thickness of the deposited lubricant layer under such deposition conditions.
In view of the criticality of the lubricant topcoat, there is a continuing need for improved lubricant stiction and wear performance. There is also a need for an improved process of uniformly applying a topcoat lubricant to the surface a recording media to achieve optimum lubricant performance.